(a) Field of the Invention
The invention relates to seven novel STR markers for DNA fingerprinting.
(b) Description of Prior Art
Creating a reliable, informative system for human identification has been long envisaged in forensic science. Polymorphism at the DNA level provides information regarding the segregation pattern of parental chromosomes during the mating process and hence discloses a person's genetic identity and thus, becomes a powerful tool for DNA fingerprinting. The information extracted from a specific DNA marker can be measured by the frequencies of each allele, and its heterozigosity and matching probability in a population. When several markers are being used together in a fingerprinting procedure, the global informativeness of the system depends on the informativeness extracted from each individual marker. Higher informativeness can only be obtained if more markers or more informative markers are used.
The Southern blot technique has been used to analyze restriction fragment length polymorphism (RFLP), a highly informative system which, however, requires considerable amounts of DNA and long periods of time to obtain, analyze and interpret the results.
The Polymerase chain reaction (PCR) has been widely used since the late 80s and proved to be a highly efficient and sensitive method to disclose and analyze DNA polymorphism. Most markers having been so far analyzed by PCR are of STR (Short Tandem Repeats) polymorphism. In a STR marker, the polymorphism arises from the number of repeats of short stretches of DNA. The number of repeats varies between individuals in the general population and thus provides a source for human identification at the DNA level. Ordinary PCR analyzes one marker at a time. More recently, primers were pooled and multiple markers were amplified in one PCR reaction. Since optimized multiplex PCR consumes considerably less reagent and time for same quality results, it greatly improves DNA fingerprinting procedures. The STR markers analyzed using multiplex PCR techniques proved to be fast, reliable and cost effective.
Markers and multiplex systems have been formulated by different suppliers for DNA forensic studies or paternity testing. The matching probabilities of individual systems reach a level of 1 in 1.times.10.sup.8 -10.sup.9. These multiplex systems combine the same 8 to 9 markers with one or two markers differing from one system to another. The need for a unique, independent and highly informative marker system was overdue. Its availability will not only strengthen the existing DNA forensic/paternity testing services, but also provide an independent counter-expertise often required in various situations.